Thanks for the encouraging words, guys.
In the meantime I did some tests with this model. Initially I edited and textured it in 3ds max, so I worked a bit on the textures and rendered an animation in Max using the inbuilt Mental ray renderer. In this particular case (ISS in space) I found that it's a lot easier to get much better results rendering the station in Max than in TG. Of course this is no surprise, since TG is a fantastic program with landscape rendering as main purpose, and it does a great job, and I'd say, it's a great additional feature that you can render objects with special materials in TG as well, so this is no complaining!!!!!